Peony

More than ten years ago I was given a piece of peony. This was a bit from a very old plant that had been in my parents' garden for as long as I can remember. I planted it in the garden and it seemed to do OK. It didn't thrive but it did flower for a few years.

It is still alive, but hasn't flowered for about four or five years. This is a shame as the flowers are lovely red doubles (I don't know what variety it is though), and I would like to know if there is anything I can do to get it going again. It's currently in full sun from about midday. The soil isn't great but I have an almost unlimited amount of horse manure at my disposal and I do put this around the garden regularly to try to improve things a bit.

Should I move it? Or is it just too old?

I do have another peony in similar conditions to the red one and that is doing really well.

I've had the same problem for the last 10 years or more, with lots of healthy leaves but no flowers. Have tried moving the plants to different parts of the garden all to no result. Some say they are planted too deep, but I've taken soil from around the stems, and that doesn't work either. Some years I get small buds but they turn black and drop off. I don't know what I'm doing wrong, unless they don't like my soil, good on top but clay about a foot down. I've just left them alone with fingers crossed each year that they might just fancy showing me a flower. All mine are the pink ones.